1. Technical Field
This disclosure relates to new organic dyes that are covalently bonded multimers or higher order symmetrical structures in which one or more dye units may optionally contain deuterium substitutions. The disclosed dyes may be particularly useful for optical coatings, new optical nanomaterials, high density storage devices. The structural and optical characteristics of the disclosed dyes provide avenues for increased information-content through surface-enhanced Raman resonance spectroscopy.
2. Description of the Related Art
Reactive fluorescent dyes have many important applications including photonic technology, specifically as active media within systems requiring syntonizable lasers, photo- and opto-electronic devices such as solar energy conversion, microscopic non-linear optical devices, and molecular probes in biochemical systems. Commonly used fluorescent dyes include, but are certainly not limited to Rhodamine (R6G), Crystal Violet (CV), and Nile Blue. Other dyes and their synthetic derivatives have been studied in optoelectronic devices include cyanin, ruthenium-based dyes, isophorone derivatives, perylene dyes, anthracene dyes, BODIPY dyes, porphyrin and Azoaromatic polymers.
Among those fluorescent dyes, R6G has been widely studied and applied for thin film lasers. For example, R6G has been incorporated into transparent and porous SiO2 thin films. The resulting R6G/SiO2 composite thin films do not disperse light and therefore can be used for integration into optical and photonic devices. A high order of R6G non-covalent dimers has been observed during the aggregation process of R6G laser dye intercalated in supported thin films of Laponite clay.
Some fluorescent and non-fluorescent dye dimers that display unique optical properties have been studied in various areas. For example, synthesized porphyrin dimers showed efficient electron injection into TiO2 in dye-sensitized solar cell based energy conversion. Hoechst dimers have also been prepared and shown to either bind dsDNA or form bridges between two dsDNA chains. Tethered merocyanine dimers displayed novel solvatochromic effects compared to the corresponding monomers. Recently, a reactive and bioreducible thiol-containing tetramethylrhodamine dimer was synthesized and proved useful as a dithiol reduction-sensitive fluorescent probe in cellular tracking systems as well as a thiol-based dye labeling reagent.
On the other hand, Raman spectroscopy is becoming an increasingly practical technique because of its minimal sample preparation requirements and compatibility with biological materials in aqueous solutions. Raman spectroscopy is the measurement of the wavelength and intensity of scattered light from molecules. The Raman scattered light occurs at wavelengths that are shifted from the incident light by the energies of molecular vibrations related to the overall polarization of the system. Typical applications are in structure determination, multi-component qualitative analysis, and quantitative analysis.
More recently, Surface-enhanced resonance Raman spectroscopy (SERRS) has become an attractive technique for applications in protein, nucleic acid, and related biomarker analysis because of its unprecedented signal enhancement. For example, R6G derivatives, as monomers, have been prepared and applied to Surface Enhanced Resonance Raman Spectroscopy (SERRS) for accurate quantification of protein concentration. Accurate quantification of protein content and composition has been achieved using isotope-edited surface enhanced resonance Raman spectroscopy (IERS). The spectral signatures reflect the expected statistical distribution of isotopologue labels incorporated into proteins in a gel matrix format without interference from protein features. However, during technology transfer to an industrial setting, these R6G monomer dyes have suffered shortcomings. The interactions between R6G and nanoparticles are variable and difficult to control, which renders their Raman signals difficult to repeat. The conjugation between the R6G monomer dye, linker, and target protein is sensitive to sample conditions. Therefore, development of new R6G derivatives that can overcome shortcomings of the monomeric forms in SERRS is an urgent task for the development of IERS.
Although R6G dimer formation in solvent has been widely studied, R6G dimer aggregation has also been observed when dyes are intercalated in solid supported thin films. Covalently linked R6G molecules have not been synthesized and their optical properties in film coating and Raman spectroscopy have not yet been characterized. The optical industry has recently indicated that R6G dimers exhibit properties desirable for certain optical coating applications; for example, extremely high absorption in the light band from 500 nm to 600 nm is needed. Development of properties to meet industrial needs is therefore desirable.
Hence, there is a need for new dyes with enhanced optical features. Moreover, there is a need for new dyes that can be used as optical coatings. Finally, there is a need for new dyes as optical coatings with stronger association to substrate surfaces.